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Leonardo Rossi (INFN Genova ) on behalf of the ATLAS Collaboration IPRD10, Siena, June 7, 2010

ATLAS Status. Brief recall of the apparatus integrated luminosity and running conditions some key commissioning results perspectives Recent results ( Fido Dittus ). Leonardo Rossi (INFN Genova ) on behalf of the ATLAS Collaboration IPRD10, Siena, June 7, 2010. ATLAS.

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Leonardo Rossi (INFN Genova ) on behalf of the ATLAS Collaboration IPRD10, Siena, June 7, 2010

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  1. ATLAS Status • Brief recall of the apparatus • integrated luminosity and running conditions • some key commissioning results • perspectives • Recent results ( Fido Dittus) Leonardo Rossi (INFN Genova) on behalf of the ATLAS Collaboration IPRD10, Siena, June 7, 2010 L. Rossi – IPRD10 - Siena

  2. ATLAS • A Toroidal LHC ApparatuS: multipurpose detector designed to cover all the expected physics channels at the TeV energy scale • weight ~ 7000 tons • height 25m • length 46m • ~108 channels (90% in the tracker) η=-ln(tan(Θ/2)) L. Rossi – IPRD10 - Siena

  3. The Inner Detector Measures charged tracks trajectories and is immersed in a 2 Tesla SC solenoidal B-field Is made of 3 sub-detectors: (resolution) Pixel : 10/115 μm in Rϕ/z Silicon strip(SCT):17/580 μm Transition Radiation Tracker (TRT):130μm in Rϕ ID covers : |η| < 2.5 (2.0 for TRT) with 3 Pixel measurements, 8 SCT and ~30 TRT. Designed for: - etrack>90% (p) and 99% (m) - σpT /pT = 0.05% pT ⊕1% and - s(ip) = 10mm at large momenta L. Rossi – IPRD10 - Siena

  4. Calorimeters • Energy measurement (and if there is unbalance, ie. ET miss) • EM calorimeter (LAr): • Precise measurement of e,g energy (+ hadrons (HEC, FCal) beyond Tile acceptance) • coverage |η|< 4.9 • Hadronic calorimeter (Tile): • energy deposit of hadrons • coverage |η|<1.7 L. Rossi – IPRD10 - Siena

  5. m spectrometer • Immersed in a torodial magnetict field (3x8 SC toroids) in air  Bdl ~ 8 Tm • Precision chambers and trigger chambers • MDT (Monitored Drift Tubes) • RPC (Resistive Plate Ch.) • CDC (Cathode Drift Chambers) • TGC (Thin-Gap Chambers) • coverage |η|<2.7 barrel end-cap L. Rossi – IPRD10 - Siena

  6. Detector is up and running 99.5% 100% After Jan 2010 shut-down fix L. Rossi – IPRD10 - Siena

  7. Beam is clean 0.9 TeV 7 TeV 45mm-x 70mm-y 7 TeV and stable 18/5/2010 L. Rossi – IPRD10 - Siena

  8. Experimental conditions are very clean too (example at 900 GeV) excellent vacuum Raw MBTS trigger (background<10-2) Asking for a reconstructed vertex drops bkgnd by O[103] • b* =2m from April 22, minimum for 2010 run • Lumi increase with • bunch intensity  1.5 1011 (~nominal)  pileup • more bunches L. Rossi – IPRD10 - Siena

  9. Multi-vertex events have been reconstructed already (commissioning is simpler without, but we better get used...) L. Rossi – IPRD10 - Siena

  10. The integrated luminosity collected so far Add most recent plot of integrated lumi from https://twiki.cern.ch/twiki/bin/view/Atlas/RunStatsPublicResults2010 • We have entered the high-pT domain at last! L. Rossi – IPRD10 - Siena

  11. van der Meer scan for absolute luminosity measurement • it will provide measurement with 10% accuracy (now 30%) LUCID online plots LUCID online plots x-scan y-scan beam spot ~ 35mm L. Rossi – IPRD10 - Siena

  12. Trigger for start-up (min-bias) ATLAS trigger has 3 levels of increasing selectivity and able to handle 40MHz collisions (storing ~ 250Hz). The inital trigger was much simpler: based on “beam is passing” (= BPTX) and “particles in a region of the solid angle” (=MBTS). BPTX is unbiased and was pre-scaled to measure the MBTS efficiency. BPTX= electrostatic beam pick-up 175m from ATLAS MBTS= Minimum Bias Trigger Scintillator, mounted on EC LAr at 3.5m from IP, covers 2.1< |η|< 3.8 with 16+16 counters. BPTX MBTS Collision event at 900 GeV. The MBTS counters above threshold are shown in yellow. L. Rossi – IPRD10 - Siena

  13. Trigger evolution • for L>5 1027must prescalemin-bias and activate more selective triggers 1000 MBTS_1 (unprescaled) MBTS_1 (prescaled/15) 100 ZDC (prescaled/15) 2 1028 EM2 10 Jet5 m0 1 Overall trigger rate: 250 Hz (400 MB/s) L. Rossi – IPRD10 - Siena

  14. The trigger strategy must evolve with luminosity (see the case for the m) • Use lower lumi samples to understand and tune triggers (timing, efficiency, control samples, etc.) L. Rossi – IPRD10 - Siena

  15. e.g. trigger threshold in the calorimeters ok and understood (vs simulation) Data/MC agreement on ET within 5% tigger-off-line correlation Low and sharp thresholds Jet trigger EM trigger L. Rossi – IPRD10 - Siena

  16. B-tagging @ 900 GeV Apply simple vertex b-tagger to 900 GeVMinBiasdata In “loose” mode, most tags are Ks. Distributions of impact parameters for tracks in secondary vertices agree well with MC simulations (left).Running the tagger in “standard” mode, find 9 events out of ~ 400K with significant positive decay length, one of which looks like a heavy flavour candidate: L. Rossi – IPRD10 - Siena

  17. Comparison data-MC at 7 TeV • Track variables • All details (including missing modules) are included as well as the beam spot. • Excellent agreement L. Rossi – IPRD10 - Siena

  18. Jets • Distributions for pT(jet)>20 GeV(AntiKt R=0.6). Jet energy at the electromagnetic scale • Min.bias trigger, lumi~350mb-1 • Good agreement L. Rossi – IPRD10 - Siena

  19. Jets of 310GeV e 350 GeV (electromagnetic scale), Df~176 degrees L. Rossi – IPRD10 - Siena

  20. Jets (hadronic scale) • Energy integrated over a cone R=0.2 around an isolated track divided by the track momentum • Data/simulation comparison (at 900 GeV)  validation of the hadronic scale in simulation and base to build-up the overall jet energy scale • Agreement within ~5% L. Rossi – IPRD10 - Siena

  21. ETmiss • Calculated using the clusters after noise suppression and at the em. scale • Min.bias trigger, lumi~110mb-1 • Excellent agreement over 6 orders of magnitude.... L. Rossi – IPRD10 - Siena

  22. Highlights and perspectives (see also F.Dittus talk) • After rediscovering the physics of the sixties (K0s, L) • and of the seventies (D*, J/y) • ATLAS is now affording the physics of the eighties (W,Z) L. Rossi – IPRD10 - Siena

  23. ….and looks forward for the physics of the tens. • We started a very long run (~18 months) aimed at an integrated luminosity of 1 fb-1 (100 pb-1 for end 2010) at 7 TeV. • The experiment performs according to design specifications and the understanding of the apparatus and MC tools is excellent (and beyond expectations in this early phase). • ATLAS will then become competitive with CDF/D0 during the coming run especially for the very highpTphenomena. J.Stirling http://projects.hepforge.org/mstwpdf/plots/plots.html L. Rossi – IPRD10 - Siena

  24. backup L. Rossi – IPRD10 - Siena

  25. Expected number of events in ATLAS for 100 pb-1 after cuts J/ψμμ Wμν Zμμ ttμν+X ttμν+X inside peak (strong cuts) L. Rossi – IPRD10 - Siena

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